7. Project Summary/Abstract Despite surgical and medical advances, the prognosis for patients with high-grade gliomas remains grim. To address this challenge, we propose a continuation of a research project that combines innovative nanomedicines with convection-enhanced delivery (CED). CED is a local drug delivery technique in which therapeutic agents are infused into the brain through catheters over a period of hours to days: this approach provides large distribution of therapeutic agents in the target region of interest. In our recent work, we have demonstrated that CED of brain-penetrating nanoparticles loaded with chemotherapeutic drugs produces dramatic increases in the survival of animals with intracranial gliomas. The therapeutic effect is even more striking when the nanoparticles are loaded with drugs that exert high cytotoxic activity against glioma stem cells (GSCs), known as the most important cells in the development and persistence of brain tumors. In this past work, we have produced brain-penetrating nanoparticles of the simplest possible design, to facilitate clinical translation of first-generation therapies. In this renewal application, we will build on this progress by testing the effect of new nanoparticle features that should enhance their activity against brain tumors. These new features are inspired by observations about brain tumor biology: (1) adenosine receptors, which are expressed on the surface of tumor cells and tumor-associated microglia, are important regulators of the brain tumor microenvironment, and can make GSCs more sensitive to chemotherapy drugs; and (2) nanoparticles enter cells primarily through endocytosis, and thus effective endosomal escape is essential for biological activity of many intracellular agents. We used these observations to generate hypotheses, which we will test by designing and synthesizing novel polymer nanoparticles. The nanoparticles are composed of block copolymers of poly(lactic acid)-hyperbranched polyglycerols (PLA-HPG) and acid-sensitive, poly(amine-co- esters) (PACE); these novel brain-penetrating nanoparticles will be administered by CED to animals with intracranial tumors. We will test these nanoparticles in three parallel specific aims: (1) covalent attachment of adenosine to the surface of nanoparticles loaded with chemotherapy drugs to sensitize GSCs and enhance treatment of intracranial tumors; (2) incorporation of acid-sensitive PACE into nanoparticles to enhance endosomal escape and, therefore, biological activity of anti-miRs, which will be tested for synergy with chemotherapy drugs; and (3) characterization of nanoparticle toxicity, biodistribution, and cellular tropism when administered by CED. Our work on these parallel aims will lead to the development of multifunctional nanoparticles that provide enhanced tumor killing when administered by CED, and are optimized for clinical translation.